PbSnS3 is a ternary sulfide semiconductor material which has been relatively little studied in the literature. Thin films of this material were deposited on glass substrates by a thermal evaporation process and their optical properties investigated. The optical parameters were determined from the analysis of measured transmission spectra, at normal incidence, from 400-1500 nm, at room temperature. The fundamental absorption edge is placed at 1.04+/-0.05 eV and is forbidden in nature. Other absorption edges are obtained at 1.44 and 1.55 +/- 0.05 eV, with a nearby direct one at 1.68 +/- 0.05 eV. The peaks at 1.44 and 1.55 eV have been independently confirmed by the spectral photocurrent response of the films.